Covid contagion: duration, incubation, before symptoms?

Covid contagion: duration, incubation, before symptoms?

Even in July 2022, Covid-19 remains an infectious disease. The original Sars-CoV-2 virus infected 3 people, the Delta variant more than 6, the Omicron variant almost 10 and its BA5 sub-variant is even more contagious. During contagion, before and after symptoms, asymptomatic…

Appearing in China in December 2019, the disease Covid-19 has infected more than one million people worldwide by the beginning of April 2020, proof of high contagiousness of his virus, the SARS-CoV-2. the transmission capacity of the coronavirus Sars-CoV-2 is analyzed by measure “R0”. This “R” corresponds to birth rate of the virus and indicates the number of people infected with positive cases of Covid-19. The higher it is, the more the disease can be transmitted. the releasing variantsfirst theAlpha from England then the Delta from India and the Omicron from South Africa changed the game because they more contagious than the original Sars-Cov-2 strain in 2020. The sub-variant BA.5 in Omicron most of France since mid-June is more contagious than BA.2, itself more transmissible than Omicron’s BA1 sublineage WHAT “Demonstrated the evolutionary capacity of the virus to be able to evade vaccines, simultaneously increasing its transmission” Infectious disease specialist Anne-Claude Crémieux explained to FranceInfo on June 22. At the end of July, the 7th wave descended with a birth rate of the virus below the threshold of 1 (one contaminated person infects less than another). Public Health France also reported a increasing the proportion of Covid infections as of December 2021. How many days are you contagious? when did you test positive for covid? 5 days? 10 days alone time? Are we? contagious if there are no symptoms ? During the incubation period? Focus on knowledge.

Effective rate of reproduction of the Covid virus in France on July 23, 2022
Effective rate of reproduction of the Covid virus in France on July 23, 2022 © Gouvernement.fr

What is the definition of contagion?

The word “contagion” comes from Latin “cum” which means “with” and “tangere” to “touch”. In medical language, contagion is defined as the transmission of an infectious agent and, if possible, the corresponding disease, from an infected subject to a healthy individual, through direct contact (skin, mucous membrane) or indirect (airborne transmission (saliva, postillions). …), digestion…).

The Sars-CoV-2 virus is spread primarily through case of close contact with an infected personthrough small particles of liquid that are released through the mouth hope through the nose when the infected person coughs, sneezes, talks or take a deep breath. “You can also contract Covid-19 if the virus enters the mouth, nose or eyesa more likely situation when people are in direct or close contact (less than a meter away) with an infected person” says the WHO. You can also get dirty if we touch our eyes, nose or mouth before washing your hands, after touching a contaminated surface. the The transmission of the virus increases the content of the contentsuffocation and inadequate ventilation.

Duration: what is the Covid contagion period?

The infectious phase of a patient who is positive for Covid-19 in the first place 8 days on average and started about 2 days before symptoms start. With the Omicron variant, “replication is fasterconfirmed by Professor Alain Fisher of the head of the Vaccine Strategy Council for France, to Les Echos. So, everything is shortened, including the symptomatic – or asymptomatic phase but contagious.

ACCORDING the study of Japanese researchers published in January 2022, it it is unlikely that vaccinated Omicron cases will shed infectious virus 10 days after diagnosis or the appearance of their symptoms (as in the case of the original virus, editor’s note). The amount of viral RNA (or “viral load“) the maximum 3-6 days after the diagnosis (test) or 3 to 6 days after the onset of symptomsthen gradually decreased over time. We should be like this contagious for a shorter time (6 days compared to ten) and not necessarily before the onset of symptoms of the Omicron variant.

How contagious is the Omicron variant?

The Omicron variant became the majority in France at the end of 2021 in just a few weeks. The number of infections doubled every 2-3 days in late November-early December, much faster than the Delta spread. According to studies reported in French Public Health, “Omicron is about 3 times more transferable than Delta”. “A professor of medicine in the United Kingdom claims that, without obstacles, the R0, the birth rate it’s almost 10“announced epidemiologist Éric d’Ortenzio of Inserm to TV5Monde, on December 31. His incubation period also shorter: “Copying is faster, confirmed Professor Alain Fisher at the head of the Vaccine Strategy Council for France, in Les Echos. So, everything is shortened, including the symptomatic – or asymptomatic phase but contagious.” ACCORDING a Japanese study published in January 2022, the high viral load 3-6 days after Omicron diagnosis (test) or the onset of its symptoms. Most of the Omicron sub-variant BA.2 in France until the beginning of June is “more infectious than its predecessor” (BA1) as Professor Arnaud Fontanet showed at France Inter on March 14. about 30% what else And the subvariant BA5 now majority”better than BA.2″ WHAT “Demonstrated the evolutionary capacity of the virus to be able to evade vaccines, simultaneously increasing its transmission” Infectious disease specialist Anne-Claude Crémieux explained to FranceInfo on June 22.

What is the incubation period for Covid?

Incubation consists of the period between the contamination of the virus and the appearance of the first symptoms. The median incubation period for Covid-19 was initially 5 days but has been reduced to Omicron. As Professor Yazdan Yazdanpanah explained to the Scientific Council of BFM-TV on January 2, 2022,we are in front of a variant with duration (incubation, editor’s note), before the onset of symptoms, which is from 5 to 3 days”. Thus we can be in contact with the virus and there are first signs of contamination after three days. During this time, the person can be contagious.

The viral load increases during the first week of illness.

Are you contagious before the symptoms of Covid-19 start?

“According to the laboratory data, this is the main one before infected people develop symptoms (ie two days before the appearance of symptoms) and at the beginning of the disease they are the most contagious.“There is explained by the World Health Organization at the start of the coronavirus epidemic in 2022. Now, facing the variant OmicronResearch does not show that people are contagious before their diagnosis (test) or their symptoms but rather in the first week. A British meta-analysis combining 79 studies on Sars-CoV-2 (5340 people) published on November 19, 2020 in the scientific journal The Lancet has shown that the viral load of Sars-CoV-2 coronavirus in the upper respiratory tract peak during first week of illness.

How long are you contagious after symptoms start?

After the 5th day, the viral load decreased.

According to the English authors of the study of Lancet published in November 2020, the The peak of contagiousness of a person who is positive for Covid-19 is up to 5e day after the onset of symptoms. Afterwards, the viral load decreased. According to the Japanese analysis of January 2022 cases Omicronthis viral load will be maximum 3 to 6 days after diagnosis or onset of symptoms then decrease. The authors also consider this to be the case it is unlikely that vaccinated Omicron cases will shed infectious virus 10 days after diagnosis or the appearance of their symptoms”. Contagion is therefore particularly strong in the first week after the onset of symptoms. It was also announced by the WHO “People who develop a severe form can be sick contagious longer”.

Can we be contagious if we have no symptoms?

A person infected with the Sars-CoV-2 virus but without symptoms is contagious and can infect other people. Similarly, someone who never develops symptoms can still transmit the virus “It’s not clear how often this happened” says the WHO. Note that if asymptomatic cases are contagious, “Covid-19 transmission usually occurs from people with symptoms” identifies the agency.

What is the risk of having Covid 2 times or more?

Public Health France reported on July 7 a increasing the proportion of Covid infections since December 2021, diffusion rate of Omicron variant (12% of confirmed COVID-19 cases in week 23 (June 6-12, 2022) are possible cases of reinfection). A high number of reinfections of Omicron after a first infection with the same variant was observed. However, the probability that a reinfection occurs after a first infection with another variant (Alpha, Delta or others) is even higher. “The The probability of reinfection increases with the age of first infection to reach a shelf about 6 months after the first infection”.

A contact case is a person who comes into contact without protective measures (such as a type 1 mask) with a person who is positive for Covid. The longer and closer the contact, the greater the risk of contamination (more than 15 minutes, less than two meters)lined up at the Ministry of Health. A contact person should be tried on D+2.

Sources:

The SARS-CoV-2 variant, Omicron, has shown rapid replication in primary human nasal epithelial cultures and effectively uses the endosomal route of entry. Thomas P. Peacock1. Department of Infectious Disease, Imperial College London, UK, W2 1PG

Recommendations related to vaccination strategy. The Senate press conference Thursday, July 1, 2021.

Covid-19 – Vaccinable? Decide with your doctor. January 29, 2021. AVAILABLE

Vaccination against Covid-19: transparency, pragmatism and flexibility are the keys to an effective campaign. Press release. November 9, 2020. AVAILABLE.

Rapid responses in the context of Covid-19 – First line care for patients with suspected Covid-19. Validated by the College on June 18, 2020. Updated on November 5, 2020. HAS.

How is COVID-19 transmitted? July 9, 2020. WHO.

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